docs: def iter_regions(self):
          """
          Return an iterable list of all region files. Use this function if you only
          want to loop through each region files once, and do not want to cache the results.
          """
          # TODO: Implement BoundingBox
          # TODO: Implement sort order
          for x,z in self.regionfiles.keys():
              close_after_use = False
              if (x,z) in self.regions:
                  regionfile = self.regions[(x,z)]
              else:
                  # It is not yet cached.
                  # Get file, but do not cache later.
                  regionfile = region.RegionFile(self.regionfiles[(x,z)], chunkclass = self.chunkclass)
                  regionfile.loc = Location(x=x,z=z)
                  close_after_use = True
              try:
                  yield regionfile
              finally:
                  if close_after_use:
                      regionfile.close()